Dataset Information

Regulation of phospholipase D isoenzymes by transforming Ras and atypical protein kinase C-iota.

ABSTRACT: The activation of phospholipase D (PLD) by transforming Ras is well documented. Although two distinct PLD isoforms, PLD1 and PLD2, have been cloned from mammalian cells, it has remained unclear whether both isoenzymes are activated by Ras and, if this is the case, whether they are stimulated by a common mechanism. In the present study we show that expression of transforming Ras in HC11 mouse mammary epithelial cells enhanced the activity of endogenous PLD. Co-expression of Ras with either PLD1b or PLD2 resulted in elevated activities of both PLD isoenzymes in HC11 cells, indicating that transforming Ras was capable of activating both PLD isoforms in vivo. Ras-induced activation of PLD was resistant to the protein kinase C (PKC) inhibitor GF109203X, which preferentially affects conventional- and novel-type PKCs, but sensitive to Ro-31-8220, which inhibits atypical PKCs more effectively. Co-transfection of atypical PKC-iota with either PLD1b or PLD2 led to a selective activation of PLD2 by PKC-iota, whereas PLD1b was not affected. PLD1b, however, was found to be a potent activator of PKC-iota, whereas PLD2 was less effective in this respect. The data suggest that PKC-iota acts upstream of PLD2 and that PLD1b is implicated in the activation of PKC-iota. The data are discussed as indicating a putative signalling cascade comprising Ras-->PLD1b-->PKC-iota-->PLD2. Evidence for the implication of this pathway in the transcriptional regulation of cyclin D1 is also presented.

SUBMITTER: Mwanjewe J

PROVIDER: S-EPMC1222137 | biostudies-other | 2001 Oct

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:TGF-beta (transforming growth factor-beta) is implicated in the pathogenesis of diabetic nephropathy. We previously demonstrated that up-regulation of type II TGF-beta receptor (TbetaRII) induced by high glucose might contribute to distal tubular hypertrophy [Yang, Guh, Yang, Lai, Tsai, Hung, Chang and Chuang (1998) J. Am. Soc. Nephrol. 9, 182-193]. We have elucidated the mechanism by using cultured Madin-Darby canine kidney cells. Enhancer assay and electrophoretic-mobility-shift assay were used to estimate the involvement of transcription factors. Western blotting and an in vitro kinase assay were used to evaluate the level and activity of protein kinase. We showed that glucose (100-900 mg/dl) induced an increase in mRNA level and promoter activity of TbetaRII (note: 'mg/dl' are the units commonly used in diabetes studies). The promoter region -209 to -177 appeared to contribute to positive transactivation of TbetaRII promoter by comparing five TbetaRII-promoter-CAT (chloramphenicol acetyl-transferase) plasmids. Moreover, the transcription factor AP-1 (activator protein 1) was significantly activated and specifically binds to TbetaRII promoter (-209 to -177). More importantly, we found that atypical PKC iota might be pivotal for high glucose-induced increase in both AP-1 binding and TbetaRII promoter activity. First, high glucose induced cytosolic translocation, activation and autophosphorylation of PKC iota. Secondly, antisense PKC iota expression plasmids attenuated high-glucose-induced increase in AP-1 binding and TbetaRII promoter activity; moreover, sense PKC iota expression plasmids enhanced these instead. Finally, we showed that antisense PKC iota expression plasmids might partly attenuate a high-glucose/TGF-beta1-induced increase in fibronectin. We conclude that PKC iota might mediate high-glucose-induced increase in TbetaRII promoter activity. In addition, antisense PKC iota expression plasmid effectively suppressed up-regulation of TbetaRII and fibronectin in hyperglycaemic distal-tubule cells.

Dataset Information

Regulation of phospholipase D isoenzymes by transforming Ras and atypical protein kinase C-iota.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets